1. Field
The disclosure relates to techniques for programming the frequency of a clock signal for a boost converter.
2. Background
Boost converters are commonly used in electrical devices to boost a voltage from one level (e.g., from a battery source) to a higher level. Conversely, buck converters are used to step down a voltage from one level to a lower level. In certain types of applications, e.g., in an envelope tracking (ET) system for efficiently supplying a radio-frequency (RF) power amplifier (PA), boost and buck converters may be jointly provided to furnish the power supply to the PA. In particular, the boost converter may provide a boosted voltage when necessary to enable the positive rail of the PA to rise above the battery voltage, while the buck converter may provide a low-frequency component of the PA supply voltage less than the battery voltage.
Both boost and buck converters commonly incorporate a plurality of switches that are driven by boost and buck clock signals, respectively. For example, the boost clock signal may control the switches of the boost converter to set the output voltage to a target boost voltage. Similarly, the buck clock signal may control the switches of the buck converter to set the output voltage to a target buck (stepped-down) voltage. In general, the buck and boost clock signals have requirements that are independent of each other. For example, the frequency of the boost clock signal should be limited to a predetermined frequency range that is partly a function of the target boost voltage, which is generally independent of the target buck voltage. Nevertheless, it would be desirable to synchronize the boost clock to the buck clock, to avoid the need to generate multiple independent clocks in a single system.
It would thus be desirable to provide techniques for generating a boost clock signal synchronous with a buck clock signal, which also ensure that the boost clock frequency is within a predetermined frequency range optimized for a particular target boost voltage.